1. Field of the Invention
The present invention generally relates to a group control apparatus for elevators.
2. Discussion of Background
With the advent of microcomputers, apparatuses for controlling the raising and lowering of elevators, or controlling hall assignments for respective elevators, have undergone tremendous changes. Conventional elevator control apparatuses mostly use relay control circuits. When the number of kinds of the elevator control functions increases, the number of relays correspondingly increases. Such an increase hinders the drive for smaller weight, lower cost, and lower power consumption. However, these problems are solved through an elevator control apparatus utilizing a compact, high performance microcomputer. The use of a microcomputer not only solves the above problems but also assists design and development of group control apparatuses and, in result, versatile and flexible elevator control has become possible.
Microcomputers may be applied to both a single unit control apparatus, which controls a single elevator (single elevator cage), and a group control apparatus, which totally controls a plurality of elevators (several elevator cages). As is well known, a group control apparatus functions to provide higher operational efficiency and better service to passangers or users when a plurality of elevator cages operate in a single system. More specifically, a group control apparatus has a hall assignment control function. With this function, in response to a hall call from the elevator hall on a certain floor, the microcomputer immediately selects an elevator cage for optimal service, so that the selected elevator cage quickly responds to the hall call. The group control apparatus also has an emergency operation control function in case of fires or earthquakes, and a rush-hour control function for providing optimal service during rush-hour. With the rush-hour control function, for example, the number of journeys of each elevator cage is increased within a specific time range.
In an elevator system using a conventional group control apparatus, when a hall call is generated upon depression of the hall button of a specific floor by a user, the hall call is registered in a hall call registration unit. The hall call registration unit supplies the hall call to the group control apparatus. The microcomputer in the group control apparatus selects an elevator which can reach the called floor in the shortest time, in accordance with the present cage positions of the respective elevators, with the cage call registration state, with the operation state of elevators and the like. The group control apparatus then registers the hall call in the single unit control apparatus for the selected elevator. Upon this hall call registration, the single unit control apparatus causes the corresponding elevator cage to go to the floor from which the hall call has been generated.
However, with such a conventional system, when the hall call registration unit fails so that a required hall call registration and data transmission are prevented, a hall call signal from the hall-called floor cannot be transmitted to the group control apparatus, and group control is thus disabled.
In this respect, the hall call registration unit is a determining factor in the reliability of conventional systems. In other words, a failure of the hall call registration unit results in breakdown of the overall group control system.
An example of such a conventional system is disclosed, e.g., in U.S. Pat. No. 3,851,735 (Winkler et al.) issued on Dec. 3, 1974. The contents disclosed in this U.S. Patent are incorporated in this application.
A microcomputer in an elevator group control apparatus requires a number of input/output signal lines. This is because the elevator control apparatus must process several hundreds of signals, including those from a position indicator, a hall registration unit, a lantern chime, and so on, mounted at each floor, and those from a cage call registration unit, a position indicator, an operation mode switch and so on, mounted in each elevator cage.
Since parallel signal transmission is adapted in a conventional elevator control apparatus, all signal lines provided for respective transmitted signals are directly connected to the I/O ports of the microcomputer. From this, in order to allow signal transmission between the microcomputer and each device on each floor, the amount of wiring in the elevator path is enormous. This has created problems of the large amount of space and costly installation operation required for wiring ducts. As for signal transmission between the microcomputer and each device in each cage, the number of tail chords (signal cables) required is also large. With the recent trend toward taller buildings, this has presented problems of complex elevator installation and maintenance operations.